Chemical testing device with a sample chamber having a piston therein with a chamber sealing element thereon

ABSTRACT

A testing device (10) for testing the level of a selected chemical in central heating system water in a central heating system circuit comprises: a sample chamber (14) for holding a sample of central heating system water to be tested, the sample chamber (14) being connectable (12) to the central heating system circuit to allow fluid to pass between the central heating system circuit and the sample chamber (14); means (16) for controlling filling of the sample chamber (14) with central heating system water from the central heating system circuit, and emptying of the sample chamber (14); at least one valve (18) for isolating the sample of central heating system water from the heating circuit during testing; and optical testing apparatus including a light source (20) and a detector (22), for measuring an optical property of the sample of central heating system water isolated within the sample chamber (14) and thereby making a determination as to whether or not the level of the selected chemical in the water is greater than a predetermined threshold level.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a United States National Stage ofInternational Patent Application No. PCT/EP2018/070497, filed on Jul.27, 2018, which in turn claims priority to Great Britain PatentApplication No. 1712175.7, filed on Jul. 28, 2017. The entiredisclosures of the above patent applications are hereby incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates to measuring the level of a chemical in asample, particularly to measuring the level of a corrosion inhibitorchemical in central heating system water.

BACKGROUND TO THE INVENTION

It is well known that wet central heating systems suffer from internalcorrosion. Steel on the inside surfaces of radiators, in the presence ofwater circulating through the system and oxygen which is inevitablydissolved in the water to some extent, is prone to rust. Due tocorrosion, particles will become detached from the damaged internalsurfaces of radiators and become entrained in the system water. Theseparticles can then cause damage to boilers, especially modernhigh-efficiency boilers which have very narrow channels in the heatexchanger. The presence of the particles also reduces the efficiency ofheat transfer, leading to higher fuel use.

Managing this problem is therefore important to prevent premature boilerfailure and ensure efficient operation. The amount of particulatecontamination in system water can be reduced by the use of a magneticfilter, which continually captures particles and removes them from thesystem flow. Filters are available which are effective to remove bothmagnetic and non-magnetic particles—see for example GB2508257.

However, using a magnetic filter on its own will not prevent corrosionand will not therefore solve the problem of magnetic particles beinggenerated in the first place. In a system which is particularly prone tocorrosion, the volume of particles being added to the system water mayexceed the rate at which they can be removed by a magnetic filter with areasonable service interval. Best practice for ensuring an efficient andreliable system therefore includes dosing the system water with aninhibitor chemical, to reduce corrosion and therefore reduce the rate atwhich particulate contamination builds up in system water. In principle,a sealed system correctly dosed with an inhibitor can remain stable formany years. However, factors which vary between systems mean that overtime, the inhibitor chemical can become diluted and/or degrade. One wayof managing this is simply to use a “rule of thumb” to top up theinhibitor in a system by adding a bottle say, every twelve months.Modest overdosing of inhibitor is unlikely to cause any technicalproblems, but adding inhibitor unnecessarily is expensive.

It is an object of the present invention to solve this problem byproviding a means for testing whether or not central heating systemwater is correctly dosed with an inhibitor chemical.

STATEMENT OF INVENTION

According to the present invention, there is provided a testing devicefor testing the level of a selected chemical in central heating systemwater in a central heating system circuit, the device comprising:

-   -   a sample chamber for holding a sample of central heating system        water to be tested, the sample chamber being connected to the        central heating system circuit to allow fluid to pass between        the central heating system circuit and the sample chamber;    -   means for controlling filling of the sample chamber with central        heating system water from the central heating system circuit,        and emptying of the sample chamber;    -   at least one valve for isolating the sample of central heating        system water from the heating circuit during testing; and    -   optical testing apparatus including a light source and a        detector, for measuring an optical property of the sample of        central heating system water isolated within the sample chamber        and thereby making a determination as to whether or not the        level of the selected chemical in the water is greater than a        predetermined threshold level.

The device of the invention allows for automated in-situ sample testingof central heating system water, to determine whether or not it is dosedwith the correct level of a selected chemical. The selected chemical isgenerally a corrosion inhibitor, although it is possible that theconcentration of other types of chemicals in central heating systemwater could be monitored by embodiments of the invention, if required.By using the device of the invention, the system can be kept dosed withthe correct level of inhibitor to limit corrosion, without wastinginhibitor.

Preferably, the sample chamber is emptied by returning the centralheating system water to the central heating system circuit. This ensuresthat there is no loss of pressure in the central heating system circuit.If the quantity is small enough, it may be acceptable in someembodiments to empty the water into a drain after testing, but over timethis will inevitably cause a loss of system pressure, and topping up thesystem will result in dilution of the inhibitor chemical.

Preferably, there is a single flow passage between the sample chamberand the central heating system circuit, to allow fluid to pass in bothdirections between the central heating system circuit and the samplechamber.

The sample chamber is preferably light transmissible, at least in therange of operation of the optical testing apparatus. This allows theoptical testing apparatus to be mounted outside of the sample chamber.In one embodiment, the sample chamber is made from borosilicate glass.Preferably, the optical testing apparatus and sample chamber areenclosed by a light-proof enclosure, or at least an enclosure whichsubstantially blocks any wavelengths which would interfere with theoptical testing apparatus.

The means for controlling filling and emptying of the sample chamber maybe in the form of a piston. Preferably, the piston includes a wiper sealwhich seals against the internal sides of the sample chamber. The pistoncan be retracted to draw water out of the central heating system circuitinto the sample chamber, remain retracted while testing takes place, andthen be extended to empty the sample chamber and return the water to thecentral heating system circuit. Emptying the sample chamber after eachtesting operation prevents dulling of the light-transmissible samplechamber by a build-up of dirt from the water onto surfaces of the samplechamber.

Where a piston is used, the valve for isolating the sample duringtesting may be integrated into the piston, so that when the piston is ina fully retracted position, having drawn water into the sample chamber,a sealing element on the piston seals the entrance to the samplechamber, preventing any further flow between the sample chamber and thecentral heating system circuit.

A piston with an integrated valve may include a necked-down section infront of the piston crown, to attach the valve to the piston whilstallowing water to flow into the sample chamber, around the necked-downsection. Alternatively, the piston might include a slot along one side(in principle, this may be considered an asymmetric necking-down of thepiston, in front of the crown). The necked-down section of the piston,in either alternative, will be present in the sample chamber duringtesting. The shape and optical characteristics of the necked-down pistontherefore need to be selected so that either the necked-down section ofthe piston does not interact with the optical testing apparatus, or thatany interaction is predictable so that it can be systematicallyaccounted for, or insignificant enough to be ignored. A slottedpiston/asymmetrically necked-down piston, may allow the necked-downportion of the piston to be located “out of sight” of the opticaltesting apparatus.

As an alternative, a valve may be provided independently of the piston.For example, a motorised ball valve may be provided between the centralheating system circuit and the sample chamber.

The testing process is preferably fully automatic, with control meansbeing adapted to draw water into the sample chamber (for example byoperating a motorised piston), seal the sample chamber by closing thevalve (if the valve needs to be operated independently of the piston),test the sample with the optical testing apparatus, including making adetermination as to whether or not the level of the selected chemical isacceptable, and then open the valve and empty the chamber. Preferably,there may be a time delay of, for example, ten minutes, between closingthe valve and testing the sample. This is to allow for any particulatecontamination in the sample to settle, whilst the sample is held in thestatic test chamber, so that any particles suspended in the system waterdo not affect the reading from the optical testing apparatus.

In some embodiments, a filter mesh could be provided between the samplechamber and the central heating system, in order to prevent particlesfrom entering the sample chamber. However, there are problems with thisapproach including an increase of power consumption when operating thepiston, due to the resistance caused by the filter mesh.

As an alternative, a magnet may be provided for attracting any magneticparticles which may be entrained in the water being tested. Preferably,the magnet may be movable between an in-use position where the magnetproduces a magnetic field in the sample chamber, and an out-of-useposition where the magnet is located away from the sample chamber andproduces no significant magnetic field in the sample chamber. Duringtesting, the magnet may be brought into the in-use position once thesample chamber is sealed. Any magnetic particles in the sample chamberwill then be drawn towards the magnet and removed from the main body ofwater in the sample chamber, clearing the water. Once testing iscomplete, the magnet may be moved to the out-of-use position andmagnetic particles will be returned to the water.

Temporarily holding magnetic particles using a movable magnet ensuresthat the water is clear of magnetic particles during testing. This, incombination with allowing a few minutes for the water to settle beforetesting, ensures that turbidity does not influence the testing process.At the same time, since the magnet is removed after testing, magneticparticles do not build up in the sample chamber. The device is notdesigned to permanently remove magnetic particles from central heatingsystem water, and it is envisaged that it would be used in combinationwith a magnetic filter on the heating system circuit, which is cleanedregularly. However, providing the movable magnet ensures that low levelsof magnetic particles remaining in the system water do not interferewith the testing process.

Preferably, the magnet is provided on the outside of the sample chamber,the magnet in the in-use position being disposed against the outside ofthe wall of the sample chamber, and the magnet in the out-of-useposition being disposed in a position outside the sample chamber, andspaced from the wall of the sample chamber. The magnet may be mounted ona pivoting arm to facilitate movement between the in-use position andthe out-of-use position. The pivoting arm may be arranged toautomatically pivot as the piston is operated to draw fluid into and outof the chamber, so that the magnet is in the in-use position when thechamber is full and in the out-of-use position when the chamber isempty.

The selected chemical is in most cases a corrosion inhibitor, althoughmeasurement of the level of other chemicals is possible using apparatusaccording to the invention. In many embodiments, the optical testingapparatus may measure the level of the selected chemical indirectly, inthat a tracer chemical is first added to the corrosion inhibitor (orother selected chemical), and it is the tracer chemical which isdirectly measured by the optical testing means. A tracer chemical can bechosen which has similar stability to the selected chemical (i.e. anydegradation of the tracer chemical is approximately the same asdegradation of the selected chemical), so that the quantity of tracerchemical detected in the system water is a reliable indication of thequantity of the selected chemical which is present. A fluorescent dyetracer which has been found to give good results with typical corrosioninhibitors is 1,3,6,8 Pyrenetetrasulfonic acid tetrasodium salt (PTSA).This fluorescent dye is found to be reasonably stable within typicalinhibitor chemicals, in the temperature conditions typical of a heatingsystem. When excited with a 375 nm source, PTSA exhibits fluorescence at405 nm. In a typical inhibitor, a concentration of 200-400 mg of tracerper litre of inhibitor is found adequate. This would give aconcentration of about 0.8-1.6 mg of tracer per litre of system water,when correctly fully dosed. An ‘acceptable’ level of inhibitor mighttypically be around 0.8 mg of tracer per litre of system water. When alower levels of tracer is detected then the device should indicate thata top-up of inhibitor is required.

An embodiment of an optical testing apparatus suitable for measuringfluorescence includes a light source for exciting the (tracer)chemical—where PTSA is used as described above the excitation lightsource would need to emit at least at 375 nm, and a detector fordetecting emitted light at the emission wavelength—in this example 405nm. The intensity of the detected emitted light at 405 nm is directlyproportional to the concentration of the fluorescent tracer chemical inthe sample, and so a determination can be made simply based on whetherthe intensity of the detected light exceeds a threshold or not.

Preferably, the excitation light source is an LED, and the detector is aphotodiode. In one embodiment, the excitation light source and detectorare placed at an acute angle to each other, facing into a substantiallycylindrical borosilicate glass sample chamber. As an alternative, thelight source and detector could be disposed at an obtuse angle,perpendicularly to each other or directly opposite each other.

Depending on the excitation light source and the detector used inspecific embodiments, it may be necessary or desirable to includefilter(s) before the detector to allow only light emitted from thefluorescent tracer through and to limit any interference from theexcitation source. Preferably, a narrow band LED is used, but to reducecosts a wider band excitation light source together with filter(s) onthe emitter and/or on the detector is a possibility.

The optical property of PTSA which is measured by the device isfluorescence. However, it is also possible to envisage alternativeembodiments of the invention, using different tracers or inherentoptical properties of the selected chemical, where the optical propertymeasured is, for example, absorption or phosphorescence.

It is envisaged that the device would automatically operate to perform atest, for example once a fortnight or once a month. This is frequentenough to ensure that a central heating system is not left for anysignificant period of time with inadequate inhibitor, but also at thistesting interval the device can be battery powered by, for example, aPP3 battery which will last a reasonable length of time.

A calibration element may be provided within the sample chamber.Preferably, the calibration element is moved into the sample chamberautomatically when the sample chamber is emptied, and moved out of thesample chamber again when water is drawn into the sample chamber fortesting. In a preferred embodiment, the calibration element is providedas part of the piston, so that the calibration element moves into thesample chamber when the piston extends. The calibration element in oneembodiment is a plastic part treated with a coating which causes it tofluoresce with similar characteristics to the tracer chemical used, witha known and constant intensity. Typically, calibration takes place aspart of the automated testing cycle, before each and every sample testtakes place.

The device may output the result of the test as simply as (for example)a red LED which lights to indicate inadequate inhibitor concentration,and a green LED which lights to indicate adequate inhibitorconcentration. It is envisaged that more advanced embodiments will beable to transmit test results, for example wirelessly by NFC orBluetooth® or WiFi or another radio frequency communication technology,or over wired communication channels. Some embodiments may be integratedinto a central heating system boiler in which case they may transmittest results to the boiler data management system.

Some embodiments may include data storage means, for storing historicaltest results which can be read out on output means or downloaded ontoanother device.

In some embodiments, the device could include an inhibitor reservoir andmeans of introducing inhibitor into the central heating system water.When the test indicates that the inhibitor concentration is too low, thesystem can then be automatically dosed to recover the correctconcentration of inhibitor.

As an alternative, a separate dosing device including an inhibitorreservoir and means of introducing inhibitor into the central heatingsystem water may be provided on the same heating system, the testingdevice being arranged to communicate with the dosing device to causedosing of the system water in response to a test result indicating thatdosing is required. Ideally a (wired or wireless) electronic signal canbe sent by the testing device to the dosing device to cause dosing ofthe system when an insufficient inhibitor concentration is detected.

In addition to the optical testing apparatus for determining whether theconcentration of the selected chemical is acceptable, the device mayinclude testing apparatus for testing the turbidity, pH, and/orconductivity of central heating system water in the sample chamber.Turbidity can be measured with optical testing apparatus, particularlyan emitter and a detector, which may work with a relatively broadspectrum of light. A test for turbidity ideally takes place very shortlyafter water has been drawn into the sample chamber, before any suspendedparticles have time to settle. Turbidity provides a measure of the levelof particulate contamination, and an excess might indicate that amagnetic filter in the system has reached capacity and needs to becleaned. Where a movable magnet is provided, the test for turbidity maytake place with the magnet in the out-of-use position. In someembodiments, one turbidity measurement could take place with the magnetin the in-use position, and one turbidity measurement could take placewith the magnet in the out-of-use position, the difference between thosetwo measurements being used as an indication of the level of turbiditydue to magnetic particles. pH and conductivity can be measured by knowntypes of probes, which need to be in contact with water in the samplechamber. It is important to ensure that the pH of system water is lowenough that its alkalinity will not attack aluminium surfaces within thesystem, for example aluminium radiators or boiler heat exchangers.Electrical conductivity can be a useful measure of the level ofdissolved salts in the system water, that could result in scaleformation.

According to a second aspect of the invention, there is provided amethod of testing central heating system water for the concentration ofa selected chemical, the method comprising:

-   -   drawing a sample of central heating system water into a sample        chamber;    -   waiting for a period of time to allow suspended solids to settle        out of the water in the sample chamber;    -   activating optical testing apparatus including a light source        and a detector, to measure an optical property of the sample and        thereby make a determination as to whether or not the level of        the selected chemical in the water is greater than a        predetermined threshold;    -   emptying the sample chamber.

According to a third aspect of the invention, there is provided anautomatic dosing device for dosing central heating system water with achemical, the dosing device including a fitment for permanentlyattaching the dosing device into a central heating system circuit, achemical reservoir, a passageway in the fitment between the centralheating system circuit and the chemical reservoir, a valve in thepassageway, and means for introducing chemical from the chemicalreservoir into the central heating system circuit in response to anelectronic signal.

The electronic signal may be a signal from a testing device according tothe first aspect of the invention. When the signal indicates that dosingis required, chemical will be introduced into the central heating systemcircuit from the reservoir, through the passageway. When dosing is notrequired, the valve in the passageway will be closed so that thereservoir is not fluidly connected to the central heating systemcircuit.

Working together, a testing device may test for inhibitor concentration,and in response to a signal from the testing device, a dosing device mayadd inhibitor to the system to correct an insufficient concentration.

In one embodiment, the chemical reservoir is in the form of a syringe,the syringe having a piston driven by an electronic actuator. In thisembodiment, the valve may be a check valve which allows fluid to flowfrom the reservoir to the central heating system circuit, but not in theother direction. When the piston is extended into the syringe, fluidwill be forced from the reservoir, through the check valve and into thecentral heating system via the passageway in the fitment. Increasedpressure in the syringe as a result of the syringe piston being operatedwill cause the check valve to open and allow fluid to flow into thecentral heating system circuit.

The actuator may be an electric motor. The motor may rotationally drivea screw, which in turn causes an arm to move linearly, pressing the backof the piston into the syringe, to dose the system with chemical.

In an alternative embodiment, the reservoir is pressurised to a greaterstatic pressure than the central heating system, and the valve is amotorised valve or another electronically actuated valve. For example, asolenoid valve may be suitable in some embodiments. In this embodiment,the valve may be opened for a period of time in response to theelectronic signal, and this will result in fluid flowing out of the highpressure reservoir and into the lower pressure central heating system.

The reservoir may be provided in the form of a pressurised canister,which includes a press-to-open valve on the nozzle. When fitted to thefitment of the dosing device, the canister may be held against a seat sothat the valve on the nozzle of the canister is permanently open whilethe canister is fitted. The seat is at the entrance to the passageway onthe fitment. Holding the canister in place may be achieved by a clampingarrangement which pushes the canister against the seat and retains it inposition. With the valve on the canister nozzle permanently open, itwill be the electronically actuated valve which controls flow of fluidfrom the canister into the central heating system circuit. However, whenthe canister needs to be removed and replaced the valve on the canisternozzle will close as the canister is removed.

Preferably a switch or sensor is provided to detect when the canisterhas been removed, and inhibit operation of the electronically actuatedvalve to ensure that the electronically actuated valve remains closedwhen the canister is not fitted. As an alternative or in addition, a oneway check valve could be provided to prevent any flow of fluid out ofthe central heating system circuit when the canister is removed ordepressurized.

In another alternative embodiment, the reservoir may again be providedin the form of a pressurized canister having a press-to-open valve onthe nozzle. However, the pressurized canister may be located with thenozzle against a seat so that the nozzle is closed in a restingposition. When an electronic signal is received and dosing is required,an electronic actuator may be arranged to press the canister against theseat to open the nozzle and allow fluid to flow from the canister intothe central heating system circuit. According to a fourth aspect of theinvention, there is provided a combined testing and dosing device,according to the first and third aspects of the invention.

In combination, a testing and dosing device work together to protect acentral heating system, by continually monitoring the concentration ofcorrosion inhibitor present in the system water.

DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and to show moreclearly how it may be carried into effect, preferred embodiments willnow be described with reference to the accompanying drawings, in which:

FIG. 1 shows a cross section through a first embodiment of a testingdevice according to the first aspect of the invention;

FIG. 2 shows a perspective view of the testing device of FIG. 1, with anouter casing fitted;

FIG. 3 shows a cross section through a second embodiment of a testingdevice according to the first aspect of the invention;

FIG. 4 shows a perspective view of the testing device of FIG. 3, with anouter casing fitted;

FIG. 5 shows a perspective view of a third embodiment of a testingdevice according to the first aspect of the invention;

FIG. 6 shows a cross section through the device of FIG. 5;

FIG. 7 shows a cross section through a first embodiment of a dosingdevice according to the third aspect of the invention;

FIG. 8 shows a cross section through a second embodiment of a dosingdevice according to the third aspect of the invention; and

FIG. 9 shows a cross section through a third embodiment of a dosingdevice according to the third aspect of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring firstly to FIG. 1, a first embodiment of a testing deviceaccording to the invention is generally indicated at 10. The testingdevice 10 comprises a fitment or connector 12 for connecting the testingdevice 10 into a central heating system circuit, a sample chamber 14 forholding an isolated sample of central heating system water duringtesting, means for controlling filling of the sample chamber 14 in theform of a motorised piston 16 having an integrated valve 18 for sealingthe sample chamber 14 when the piston is retracted, and optical testingapparatus including an excitation light source 20 and a detector 22.

The connector 12 is in the form of a simple T-shaped connector, allowingcentral heating system water to flow (for example) into an inlet port 24and out of an outlet port 26. In this embodiment, the connector 12 issymmetrical and so the inlet 24 and outlet 26 could be swapped, i.e.with central heating system water flowing in the other direction. Theconnector 12 connects the sample chamber 14 into the central heatingsystem circuit, so that samples of central heating system water can bedrawn into the sample chamber and tested automatically, wheneverrequired.

In this embodiment, the connector 12 is in the form of a reducing T,i.e. the inlet and outlet ports are 22 mm compression fittings, and thebranch of the T which connects to the sample chamber 14 is smaller indiameter. As an alternative to compression fittings, push-fit fittingsor any other suitable fittings may be provided, for connecting thedevice into a central heating system circuit. Also, different sizes ofdevice may be provided for central heating systems using pipe diameterslarger or smaller than 22 mm.

As an alternative to a T-shaped connector, a Y-shaped connector, or anyother suitable shape may be used.

The walls 14 a of the sample chamber 14 are made from borosilicateglass, which is transparent and highly resistant to thermal shock. Thesample chamber 14 is a substantially cylindrical tube. A flow passage 28is provided between the sample chamber 14 and connector 12, for allowingwater to pass from the central heating system circuit into the samplechamber 14, and back again from the sample chamber 14 into the centralheating system circuit.

To control filling and emptying of the sample chamber 14, the piston 16can be extended into the sample chamber to empty the sample chamber 14,or retracted to fill it. In FIG. 1 the piston 16 is shown in anintermediate position; a fully-extended position would be furthertowards the top of FIG. 1, and a fully-retracted position would befurther towards the bottom. The piston 16 includes an O-ring wiper seal16 a, which prevents any water getting behind the seal 16 a (i.e. belowthe seal 16 a in FIG. 1). The wiper seal 16 a also acts to clean theborosilicate glass walls 14 a of the sample chamber 14 after each use,to prevent dulling of the walls 14 a and a reduction inlight-transmissibility due to accumulation of dirt.

In this embodiment, the piston includes an integrated valve 18. When thepiston is fully retracted (i.e. all the way downwards in FIG. 1), thevalve 18 engages with a valve seat 18 a to seal the sample chamber fromthe central heating system circuit, and keep the water sample static andisolated.

The excitation light source 20 and detector 22 are provided at an acuteangle to each other, facing towards the sample chamber 14 on the outsideof the borosilicate glass wall. An opaque moulding 30 is provided whichhouses the borosilicate glass tube sample chamber 14, and provides amounting for the light source 20 and detector 22. The opaque moulding 30prevents any light entering the sample chamber 14 from outside, controlsthe incidence of light on the sample chamber from the light source 20,and ensures that the light source 20 and detector 22 remain in a fixedposition relative to each other, for consistency of measurements.

A stepper motor 32 is provided to move the piston 16 between theretracted and extended positions on a screw thread. Another type ofactuator, for example a solenoid or another linear actuator, may besuitable in other embodiments.

Referring now to FIG. 2, the same embodiment is shown, fitted with anouter casing 34. The outer casing encloses substantially all of thecomponents of the testing device 10, with only the connector 12extending out of the casing, for connection to a central heating systemcircuit. In addition to the components described and shown in FIG. 1,the casing 34 houses a control PCB and a battery to power the device. Insome embodiments, an AC/DC transformer may be provided either internallyof the casing 34 or externally, instead of a battery.

FIG. 3 illustrates an alternative embodiment of a testing device 10′. Inmost respects this embodiment is similar to the embodiment of FIG. 1,and like parts are labelled with like reference numerals. However,instead of the valve (18) integrated with the piston (16), thealternative embodiment uses a motorised ball valve 18′, disposed in theconnector 12, to seal the sample chamber 14 from the central heatingcircuit. The ball valve 18′ is operated by an separate motor (notvisible in the figures), and not by the stepper motor 32 which operatesthe piston 16′. As shown in FIG. 4, the motorised ball valve (18′) andits corresponding motor are housed in a separate housing 36.

The body of the piston 16 may include a calibration element which isdisposed within the sample chamber, within “sight” of the opticaltesting apparatus, when the piston is in its extended position.

Typically, the devices are adapted to follow a testing procedure as setout below. The devices will generally be controlled by electronics on acontrol PCB which may be housed in housing 34, although in someembodiments might be externally mounted, for example if the device is tobe integrated into a boiler. The control PCB may include amicrocontroller, or any other suitable type of control circuitry.

The process begins with the piston 16 in its fully-extended position,with the sample chamber empty.

First, the excitation light source 20 is switched on. This excites afluorescent coating on the calibration element which forms part of thebody of the piston 16. The fluorescent coating emits light at (forexample) a wavelength of 405 nm. The intensity of the 405 nm radiationis measured by the detector 22. Because the intensity of the excitationlight source 20 and the fluorescent properties of the coating on thecalibration element are known with some accuracy, the measurement fromthe detector 22 can be used to calibrate the device 10, effectivelyaccounting for any dirt which may have built up on the borosilicateglass walls 14 a. Once the calibration reading is taken, the excitationlight source 20 can be turned off.

The piston 16 is then retracted, drawing a sample of water into thesample chamber 14. In the first embodiment (FIG. 1), this also has theeffect of moving the integrated valve 18 to meet the valve seat 18 a, toseal off the sample chamber 14 from the central heating system circuit.In the alternative embodiment (FIG. 3), the motorised ball valve 18′will have to be operated at this stage to seal off the sample chamberfrom the central heating system circuit.

Once the water sample is in the sample chamber 14, it is left to cooland settle for a period of time. This time period may be 5 minutes, or10 minutes, or another period. The purpose of the delay is to allow anysolids to settle out of the sample, so that turbidity does not affectthe results of the test. It may also be necessary to allow the sample tocool, depending on the optical property being tested and the chemicalbeing used.

The excitation light source is then switched on to excite the sample.This results in fluorescence of the sample, depending on theconcentration of the selected chemical present. It will be appreciatedthat fluorescence is not the only optical property which can be used totest the concentration of a selected chemical. Absorption andphosphorescence are other potentially-suitable properties.

The detector then measures the intensity of emitted light at (forexample) 405 nm, which is the expected fluorescent emission wavelengthof the tracer chemical in one particular embodiment. Preferably, severalmeasurements are taken, for example three measurements over 10 to 20seconds. Taking an average of multiple measurements can help to ensureconsistent results. Once all measurements are taken, the excitationlight source is turned off.

After testing is complete, the motorised ball valve 18′ (whereapplicable) is opened, and the piston 16 is extended to empty the samplechamber 14. The wiper seal 16 a cleans the inside of the borosilicateglass walls 14 a as the piston 16 extends.

The readings from the detector 22 are assessed. In a simple embodiment,it is simply determined whether or not the level of the chemical isacceptable or not. A simple output interface might comprise a green LEDfor acceptable and a red LED for inadequate. Alternatively, the resultsmight be transferred to a follow-on system, for example a boiler datamanagement system, via a wired or wireless connection. In someembodiments, an electronic signal may be sent to a dosing device tocause dosing of the system with inhibitor, when an insufficientconcentration is detected.

Referring now to FIG. 5 and FIG. 6, yet another embodiment of a testingdevice is indicated at 10″. This embodiment is substantially identicalto testing device 10′ of FIG. 3 and FIG. 4, but includes a movablemagnet 40. The magnet 40 is provided at one end of a pivoting arm 42,and by pivoting the arm the magnet may be moved from an in-use position,in which the magnet 40 is in contact with the wall 14 a of the samplechamber 14, to an out-of-use position where the magnet is spaced awayfrom the wall 14 a of the sample chamber 14. It is the in-use positionwhich is illustrated in FIG. 5 and FIG. 6.

The magnet in the in-use position contacts the outside of the wall 14 aof the sample chamber through a hole in the opaque overmoulding. Alight-tight seal is preferably provided to prevent leakage of light intothe sample chamber. Alternatively, a light-tight external casing may berelied on to prevent ambient light leaking into the sample chamber.

As seen most clearly in FIG. 6, the pivoting arm is connected to thebody of the testing device at a pivot 44. Between the pivot 44 and themagnet 40, a spring 46 is provided which urges the magnet end of thepivoting arm away from the wall of the sample chamber, i.e. into theout-of use position. At the other (non-magnet) end of the pivoting arm,a follower 47 is provided. The follower 47 contacts a linear cam 48,which in turn moves linearly with the piston 16. The linear cam 48 ispositioned to lift the follower away from the body of the testing devicewhen the piston 16 is retracted to fill the sample chamber 14. Bylifting the follower away from the body of the testing device, themagnet 40 on the other end of the pivoting arm is moved into contactwith the wall 14 a of the sample chamber 14, against the action of thespring 46. In this way, the magnet 40 is positioned in contact with thewall 14 a of the sample chamber 14, whenever the syringe is retractedand the sample chamber is full of liquid.

The magnet attracts any magnetic particles which may be entrained in thewater sample being tested, and prevents the entrained magnetic particlesfrom adversely affecting the testing procedure.

Referring now to FIG. 7, a dosing device according to the third aspectof the invention is indicated generally at 50. The dosing deviceincludes a fitment 52 for connecting the dosing device 50 into a centralheating system circuit, a chemical reservoir 54 in the form of asyringe, and a passageway 56 between the syringe 54 and the fitment 52.A one-way check valve 58 is provided in the passageway 56. The checkvalve 58 allows fluid to flow out of the syringe 54 into the centralheating system circuit, but prevents flow out of the central heatingsystem circuit into the syringe 54.

The syringe 54 includes a piston 60, which can be extended into thesyringe 54 (i.e. moved leftwards in FIG. 7) in order to force liquidfrom the syringe 54, through the passageway 56 and valve 58, into thecentral heating system circuit via the fitment 52.

The syringe piston 60 may be pushed into the syringe body by an arm 62.The arm 62 includes a screw threaded aperture. An externally screwthreaded rod 64 passes through the aperture, and is fixed at one end tothe shaft of an electric motor 66 which in turn is fixed relative to thesyringe body 54. In this way, the electric motor can rotate the threadedrod 64 in order to move the arm 62 linearly, to extend the piston 60into the syringe 54 and force inhibitor chemical from the syringe 54into the central heating system circuit.

The syringe 54 is removable from the passageway 56 so that the syringemay be refilled with inhibitor chemical when empty. With the syringeremoved, the check valve 58 will always be closed, preventing anyleakage of water out of the central heating system circuit.

Referring now to FIG. 8, a second embodiment of a dosing device isindicated generally at 70. The dosing device 70 again includes a fitment72 for connection to a central heating system, a reservoir 74 containinginhibitor chemical, a passageway 76 between the reservoir 74 and thecentral heating system circuit, and a valve 78 in the passageway 76.However, in this embodiment the reservoir is a pressurised canister andthe valve is a motorised valve. In response to the electronic signal,the valve 78 opens and, because of the greater static pressure on thereservoir side, fluid will flow from the reservoir into the centralheating system. The valve 78 can be opened for a period of time tocontrol the amount of inhibitor chemical which is dosed into the centralheating system.

The pressurised canister 74 includes a nozzle 80 with a push-to-openvalve. A seat is provided on the entrance to the passageway 76, and whenthe canister is fitted the nozzle 80 is pushed onto the seat to hold thepush-to-open valve permanently open while the canister 74 is attached tothe dosing device 70. The canister 74 is held onto the rest of thedevice 70 and against the seat on the entrance to the passageway 76 bymeans of a clamp 82 which extends from the fitment 72, along the outsideof the canister and behind the canister, to push the canister againstthe seat. The clamp 82 may be spring-loaded to allow quick release ofthe canister. When the canister is removed, the valve on the nozzle 80will close to prevent any leakage. It is envisaged that disposablecanisters will be supplied full of inhibitor chemical, and when thecanister is empty it will be discarded and replaced with a new, full,pressurised canister.

Referring now to FIG. 9, a third embodiment of a chemical dosing deviceis indicated generally at 90. The dosing device includes a fitment 92for connection to a central heating system circuit, a reservoir 94 whichin this embodiment is a pressurised canister with a push-to-open valveon the nozzle, similar to the canister (74) of the second embodiment, apassageway 96 in the fitment between the canister 94 and the centralheating system circuit, and a check valve 98 in the passageway 96. Thecanister 94 is disposed with the nozzle 100 seated on the entrance tothe passageway 96, such that when the canister 94 is pushed towards theentrance to the passageway 96, the valve on the nozzle 100 will open andchemical will be admitted into the passageway 96, through the checkvalve 98, and into the central heating system circuit 92.

The canister 94 is held against the entrance to the passageway 96 bymeans of a clamping and actuation arrangement 102. At one end theclamping and actuation arrangement is fixed to the fitment. Aretractable member 104 extends from the fitment 92, alongside theoutside of the canister 94 (underneath the canister 94 in FIG. 9) andthen behind the canister, where it holds the canister 94 from behind. Byretracting the retractable member 104, the nozzle 100 of the canister ispushed against the seat on the entrance to the passageway 96, to openthe push-to-open valve. The retractable member 104 is retracted by anactuator 105. The actuator may be a motor with a screw threaded rod, oralternatively the actuator may be a solenoid or other linear actuator.The actuator operates in response to an electronic signal to retract therod, push the canister 94 against the entrance to the passageway 96, anddose the heating system with inhibitor chemical from the canister 94.

The testing device and dosing device may work together to protect aheating system. When the testing device detects that the central heatingsystem is insufficiently dosed with inhibitor chemical, it may send anelectronic signal to the dosing device to cause dosing of the systemwith inhibitor, to correct the dosing level before significant corrosionis allowed to occur. The testing device and dosing device in someembodiments may be combined into a single housing, and/or may share asingle fitment for connection to the central heating system circuit.

The embodiments described above and illustrated in the figures are onlyexamples of how the invention might be put into practice. Variousmodifications will be apparent to the skilled person. The invention isdefined in the claims.

The invention claimed is:
 1. A testing device for testing a level of aselected chemical in a central heating system water in a central heatingsystem circuit, the testing device comprising: a sample chamber forholding a sample of central heating system water to be tested, thesample chamber being connected to the central heating system circuit toallow fluid to pass between the central heating system circuit and thesample chamber; a piston for controlling filling of the sample chamberwith the central heating system water from the central heating systemcircuit, and emptying of the sample chamber, the piston being movable toa retracted position for drawing water out of the central heating systemcircuit into the sample chamber, and to an extended position foremptying the sample chamber and returning the water to the centralheating system circuit; at least one valve for isolating the sample ofcentral heating system water from the central heating system circuitduring testing; and an optical testing apparatus including a lightsource and a detector, for measuring an optical property of the sampleof central heating system water isolated within the sample chamber andthereby making a determination as to whether or not the level of theselected chemical in the water is greater than a predetermined thresholdlevel, wherein the valve for isolating the sample during testing isintegrated into the piston, and wherein a sealing element on the pistonseals the entrance to the sample chamber where the piston is in aretracted position, for preventing any further flow between the samplechamber and the central heating system circuit.
 2. The testing device ofclaim 1, wherein the selected chemical is a corrosion inhibitor.
 3. Thetesting device of claim 1, wherein the sample chamber is emptied byreturning the central heating system water in the sample chamber to thecentral heating system circuit.
 4. The testing device of claim 1,wherein a single flow passage is provided between the sample chamber andthe central heating system circuit, to allow fluid to pass in bothdirections between the central heating system circuit and the samplechamber.
 5. The testing device of claim 1, wherein the piston includes awiper seal for sealing against and cleaning the internal walls of thesample chamber.
 6. The testing device of claim 1, wherein the pistonincludes a necked-down section in front of the piston crown, and thesealing element being attached to the piston crown via the necked-downsection.
 7. The testing device of claim 6, wherein the necked-downsection is located asymmetrically to a one side of the piston, in frontof the piston crown.
 8. The testing device of claim 1, wherein a controlmeans is provided and adapted to control the testing device forfully-automated testing, including drawing water from the centralheating system circuit into the sample chamber, sealing the samplechamber, testing the sample with the optical testing apparatus, andopening the valve and emptying the chamber.
 9. The testing device ofclaim 8, wherein the control means is adapted to wait for a period oftime between closing the valve and testing the sample with the opticaltesting apparatus.
 10. The testing device of claim 9, wherein the periodof time is at least one minute.
 11. The testing device of claim 1,wherein the level of the selected chemical is determined indirectly, byusing the optical testing apparatus to measure a concentration of atracer chemical which has been added to the selected chemical in a knownconcentration.
 12. The testing device of claim 11, wherein the tracerchemical is 1,3,6,8 Pyrenetetrasulfonic acid tetrasodium salt (PTSA).13. The testing device of claim 1, wherein the light source and detectorare disposed at an acute angle to each other, facing into the samplechamber.
 14. The testing device of claim 1, wherein at least one filteris provided on at least one of the detector and the light source. 15.The testing device of claim 1, wherein the optical property isfluorescence.
 16. The testing device of claim 1, wherein a calibrationelement is provided within the sample chamber.
 17. The testing device ofclaim 16, wherein the calibration element is moved automatically intothe sample chamber where the sample chamber is emptied, and moved out ofthe sample chamber where water is drawn into the sample chamber fortesting.
 18. The testing device of claim 17, wherein the calibrationelement is provided as part of the piston.
 19. The testing device ofclaim 1, wherein a magnet is provided for attracting any magneticparticles entrained in water in the sample chamber.
 20. The testingdevice of claim 19, wherein the magnet is movable between an in-useposition adjacent to the sample chamber and an out-of-use positionspaced from the sample chamber.
 21. The testing device of claim 20,wherein the magnet is movable on a pivoting arm.
 22. The testing deviceof claim 21, wherein the pivoting arm is arranged to automatically pivotas the piston is operated to draw fluid into and out of the samplechamber, so that the magnet is in the in-use position where the chamberis full and in the out-of-use position where the chamber is empty. 23.The testing device of claim 1, further comprising a reservoir of theselected chemical, and a means for introducing a quantity of theselected chemical into the central heating system circuit, in responseto a determination by the optical testing apparatus that theconcentration of the selected chemical in tested water is inadequate.